Controlling error orientation to improve quantum algorithm success rates
Controlling error orientation to improve quantum algorithm success rates
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DOI：
10.1103/physreva.99.032318
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发表时间：
2018-10
影响因子：
2.9
通讯作者：
Daniel Murphy;K. Brown
中科院分区：
文献类型：
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作者：
Daniel Murphy;K. Brown
由噪声量子门构建的量子算法的成功概率无法通过比较噪声门和理想门的单参数度量来准确预测。我们通过检查具有相干误差的系统并比较由复合脉冲序列构建的双量子位门的不同选择的算法成功率来说明这一概念，其中残余门误差通过酉变换相关。因此，在任何距离测量下，所有序列相对于理想门都具有相同的误差，而该距离测量在酉变换下是不变的。然而，通过选择不影响最终结果的误差方向和在共轭受控非之间抵消的误差方向，电路的成功可能会发生很大的变化，如 Clifford 电路、编译的 Toffoli 门和量子模拟算法所示。结果指出了最小化误差和优化误差方向的效用，以及在单个算法中对相同门类型使用多个控制序列的优点。
The success probability of a quantum algorithm constructed from noisy quantum gates cannot be accurately predicted from single parameter metrics that compare noisy and ideal gates. We illustrate this concept by examining a system with coherent errors and comparing algorithm success rates for different choices of two-qubit gates that are constructed from composite pulse sequences, where the residual gate errors are related by a unitary transformation. As a result, all of the sequences have the same error relative to the ideal gate under any distance measure that is invariant under unitary transformations. However, the circuit success can vary dramatically by choosing error orientations that do not affect the final outcome and error orientations that cancel between conjugate controlled-nots, as demonstrated here with Clifford circuits, compiled Toffoli gates, and quantum simulation algorithms. The results point to the utility of both minimizing the error and optimizing the error direction and also to the advantages of using multiple control sequences for the same gate type within a single algorithm.